Hello to all. I am new here and new to a 1988 K100RS. I got it for a really low price, the engine seems to crank and run fine. In fact, I think it mostly just needs running. It rides well, shifts well and there are not many strange noises. My Intention is to go over the bike, checking for things that I have read about, change all fluids, grease splines, etc. So I am looking for a good list of things to check.

The purpose of this thread is electrical. If I may, I would like to describe the symptoms and ask if there are possibly common problems that contribute to the listed issues.

What works:
The tail and brake lights. Two separate bulbs, right?
The front running light, after bulb installation (not sure I have the correct bulb, but it works)
The left turn signals, front and rear - AFTER actually plugging together the disconnected connectors behind the front left mirror
All the dash lights work
The low position high beam flasher works

What doesnt work
Both turn signals on the right - Installed new bulbs all around
Low and High beam (again, the high beam flash position works), also all bulb leads show continuity so I think the bulb is good. Also tested headlight plug with tester, juice only to flasher.

I have read the threads about the left, headlight switch going bad so I will dismantle and check it. Could there be a common issue for the headlight and right turn signals? Or two separate issues?

Again, I will check the light switch for juice and corrosion. Where do I start with the right signal circuit?

Thanks for all the time y'all take trying to help inexperienced folks, like myself.

Philip

The Switches on the right handlebar seems like a good place to start.
I had problems with the right indicator switch on my K100 and ended up putting an extra switch on instead of having to buy a new unit.
It is just a simple push to on switch mounted in the mirror post hole and I opperate it with my index finger cost about $2 from Jaycar (radioshack).
As for the headlight if it has an on - off switch on the right try there or if no switch check under the tank at the plug and socket point for the right switch.

Here I go again...

"DeoxIT is my friend". Repeat three times loudly.

Buy some DeoxIT D-Series cleaner and go over EVERY gol-dang connector and bulb on your bike. This stuff cleans, seals and protects the connection. Wonderful stuff.

If it's not too late, be careful opening the switches as there are springs and stuff that can go flying off into the darkest recesses of your shed...never to be seen again.
Maybe take them apart inside a large clear plastic bag?

Electrics can be difficult, but trace the wires individually to see if you can find the fault.

If it's the headlight and the right indicator, as a suggestion, check the the loom is not being chaffed somewhere when the handlebars are turned from lock to lock.

Try all of the stuff suggested by K Freak and myself and get back to us.

Phillip I have read your post and you can see from what you have written that the area of concern is your right switch block, The High low beam switch on the left switchblock operates when the lights are turned on from the right switch block. Follow blakey's line with the deoxit type of cleaner and you should have an improvement, clean and assemble the right switch block and check for results. Keith P.S. you could drown the switch block with WD40 to start with, it will provide you with some idea of how much gunk has collected in there and test the switches then. Then a more thorough clean up should do it.

AUsome and straight to the point responses! Thank you, Thank you! I will proceed as suggested and report back.

I have been through electrical issues before, but on a KLR705. A much simpler bike. That turned out to be one broken connection in the harness, at the neck. It is of great value to have a focus on such a complicated bike by comparison.

Again, Thank you!

Philip

hey phillip ....nice looking bike .....

hope you find some solutions soon ......i thik we all are interested in keeping our old gals in good shape ...
some awesome folks here ...

cheers

Nice bike phillip, just do what blakey says I did and it sorted out various electrical problems that stuff is the way forward on a regular basis.

BIG D

Ok, some random testing results.

There does not seem to be a headlight on/off switch on the right controls. UK only in the wiring diagram.

There are 4 switches on the rubber handlebar dash. The ABS switch works, as does the flasher switch (but only on the left side). The "driving light" switch, to left, seems to do nothing as there are no driving lights. The blank on the right is unknown. All the switches are sticky and have wires and power to them.




There is continuity all over the place. But, there is no ground in the ground wire to the non working right front turn signal, but ground to the right rear signal is there. Broken where?

There is power and ground to all connections in the right bar controls. Also power in the left bar controls.

Question, could the flasher be partially bad? I doubt it. Still sounds like a broken wire or switch issue to me.

What does a shed relay do?

The headlight connector has ground on br, the white wire has juice, the yellow, middle wire does not, but seems to have continuity to the left control switch.

Still points to same switch?

Again, random bits to throw out to see what yall think.

Again, thanks for looking and helping!

Also, here is the diagram I am using. I have marked it up a bit if you can read it.

Also, could someone point me to directions on removing the fuel tank? I can lift the rear loose, but I am not sure of the complete, correct procedure.

Fuel and return lines on left front of tank to be undone and slipped off,2 vent lines under the tank that need to be taken off, they just slip on and can be pulled off by hand. Then tank is pulled back to clear front mounts and lifted off.

DSCR wrote:Also, here is the diagram I am using. I have marked it up a bit if you can read it.

You are using the electrical schematic of an early K (1984-1985) but yours is a 1988.
84-85 didn't have the ABS.
Most of the schematics that I posted on this forum are for the early K. (This is what I own and what I am working with)

Bert

I have a wiring diagram for late model K100 as a JPEG. I can't post it because it is 2.5MB in size. If you PM your email address to me, I can send you a link to download the diagram.

DSCR wrote:There does not seem to be a headlight on/off switch on the right controls. UK only in the wiring diagram.

This is normal for US modles. The right handlebar switch assembly for the UK has a different part number. The under tank connector in either part are the same. In the US, pins 3,4 and 7 are wired together within the connector. The lights are intended to come on with the ignition switch.

DSCR wrote:there is no ground in the ground wire to the non working right front turn signal, but ground to the right rear signal is there. Broken where?

If the bike took a spill, it is possible that the right mirror tore the wire within the harness. I think you mentioned that you had to reconnect the turn signal at the mirror. The grounding point for the right front turn signal is shared with the left front turn signal. Quick debug method. Make a jumper wire and try grounding the right turn signal. If the signal works, you've found the problem. If not, the right hand switch assembly or the flasher relay are the problem. If the problem is the wire, trace the wire to see where that wire may be broken or bypass it completely by installing a new wire.

DSCR wrote:There is power and ground to all connections in the right bar controls. Also power in the left bar controls.

sounds like the right hand control assembly is functional. might not be the problem area.

DSCR wrote:Question, could the flasher be partially bad? I doubt it. Still sounds like a broken wire or switch issue to me.

It is possible that the flasher is partially bad. The flasher relay is more than a simple relay; it's an electronic circuit. So, a blown component within the relay may exhibit strange behaviours as you are seeing. It is still a possibility until you eliminate it by testing.

DSCR wrote:What does a shed relay do?

Load shed removes power from the lighting circuit during starting so that full power is available to the starter.

DSCR wrote:The headlight connector has ground on br, the white wire has juice, the yellow, middle wire does not, but seems to have continuity to the left control switch.

Still points to same switch?

That's weird. The power is routed to the white wire when the high beam switch is flash position . There should be no connections through the high beam switch on the left switch cluster when it is in its normal position. Are you sure that you haven't accidently put the high beam switch in HIGH mode?

Most of the items that you added "Where?" in your diagram are located in the relay box under the tank. The exception is the heated grip connector which is located under the tank on the left side, buried somewhere within the wiring harness. Refer to my tutorial on adding after-market grip heaters to see a photo of where that connector is situated.

The following was posted to the BMWMOA site recently. It is relevant to your problem:

Check for corrosion on the sockets, on the shell and on the inner central contact.
Also check the bulbs themselves; not just for corrosion, but the center contact is just solder - this can wear down or deform.

A long shot but it's happened: one or more bulbs may have a broken
filament that is still touching at the break; this can sometimes be
spotted only with a magnifying glass. They're cheap, replace 'em
anyway. Try to avoid the Phillips brand; these are supplied as OEM in
many vehicles, and they're cheap for a reason.

My K100 had absolutely ZERO "service loop" and very close to zero stress
relief all along its wiring - you may have an intermittent break, the
hardest thing to nail down.

Major clues when it happens:
1) do both sides fail
2) do the front and rear both fail on one side
This should narrow down where the gremlin is hiding.

Wow, a response filled with direct
experience! Thanks, Robert! And everyone else!

Upon further review, you are correct.
The white wire at the headlight socket only has power when the flash
function is used on the light switch on the left control. Thus, the
flasher works.

The only continuity for the yellow
wire, is to the solder point in the light switch on the left control.

I am no expert, but I seem to get
continuity everywhere. Even in places that surprise me. I am sure
there is an explanation I dont yet understand. I am speaking of for
example, with a pin in the ground of the light socket, I get
continuity to all sorts of non ground things. Like the hot wire of
the turn signals and all the soldered pins for the headlight dimmer
except the yellow one.

As an aside, as suggested I jumpered
the right turn signals bypassing the bad former repairs, and still no
sign of signals on the right. The right switches all test out good
when operated while on the tester. I dont think it is the right
switch. I havent ruled the left switch as the culprit with the
headlight, however.

Turn signal summary. The “repairs
were bad in both front signals within the mirrors. I think this bike
has been dropped on both sides and repairs were mangled and ruined
the connectors connected to the harness. The receiving connectors
within the mirrors seem to be fine and test out ok. A jumpered
connection yielded no turn signals on the right. At the bare wires,
there is good ground and continuity to the rear right lamp. It seems
that closing the circuit at the right switch does not get a response
from the flasher unit, even when manually jumped. Again, the right
switch seems to function properly with the tester.

Thoughts on signals, other than getting
this tank off and somehow testing the flasher?

Is there a preferred source for
replacement pins on the loom side? Also, how do you get these dag
gummed mirrors off. It is almost impossible to plug the connectors
from the lens hole.....

Headlight summary. No clue, other than
cleaning the switch. However, manually crossing the soldered pins
has yielded no response.

I look forward to your ideas.....

Thanks for your help!

Hi,

I am looking at what circuit is common between the front right signal and back right signal. The only common element is the flasher unit. I'm thinking a test you can perform to validate the signal wiring is this:

1. Open the relay box (will require removing the tank), remove the flasher unit and disconnect the plug from the unit.
2. On the connector, locate the pins to which the "blue with black tracer" wire is connected and the "red with white tracer" is connected
3. Confirm that +12V is available on the red/white wire by measuring to ground with a volt meter.
4. if voltage is available, jumper red/white to blue/black momentarily. This should power just the right hand side signal lamp circuit.

If the wiring to the signal lights is intact, the right signals and dash indicator should illuminate. If the wiring is broken, one or both signal lights will fail to illuminate.

If the lights illuminate, the problem is the flasher unit. If the lights fail to illuminate, the problem is in the wiring loom and you need to trace wires.

There may seem to be continuity to many places when measuring with a voltmeter, but you have to confirm whether you are seeing zero ohms or extremely low ohms. Many of the loads presented on the bike are low, giving the impression of continuity. Are you using an audible continuity tester or an ohmmeter? Is it a good quality multimeter, like a Fluke? Cheap multimeters may be incapable of discerning between low resistance loads and continuous circuits.

Other tests that you may want to perform while the flasher is out are:
1. operation of the left hand signal switch. Check for continuity to ground from the "blue with brown tracer" contact when the left signal button is pressed
2. operation of the right hand signal switch. Check for continuity to
ground from the "blue with yellow tracer" contact when the right signal
button is pressed
3. operation of the signal cancel switch. Check for continuity to
ground from the "brown with white tracer" contact when the left hand canel button is pressed

Have you checked this page?
I have a detail of each of the major components of the electrical circuit. As I colored the wires, it is quite easy to follow them. The schematics are for the early K100, but I believe that lights and flashers are the same for all the K100s.
Here is an example of the connections for the flasher functions. (every brown wire is a ground). The blue/green wire going to the speedo is the signal to cancel the flashers (I believe after 30 seconds when riding over 30km/h)


Here are the connections on the instrument cluster:



Bert

wow bert....... that is awesome .

never seen that before .......omg ...thanks

The link for this page is right under the last 50 posts on the portal page.
I guess it's there for 2 years......

lol bert ...yes i had noticed it .....i was just in awe of the work ....

such a great resource for all of us ....

The answer is.....No, I had not found that AUsome tool. Wow! I am pretty good at following plain'ol diagrams, at least on a computer where I can zoom in. But, this is THE diagram tool of all diagram tools! Fantastic work!

Thank you, Bert!